Three-dimensional memory device having a shielding layer and method for forming the same

ABSTRACT

Embodiments of three-dimensional (3D) memory devices having a shielding layer and methods for forming the 3D memory devices are disclosed. In an example, a method for forming a 3D memory device is disclosed. A peripheral device is formed on a substrate. A first interconnect layer including a first plurality of interconnects is formed above the peripheral device. A shielding layer including a conduction region is formed above the first interconnect layer. A second interconnect layer including a second plurality of interconnects is formed above the shielding layer. The conduction region of the shielding layer covers an area of the first and second plurality of interconnects in the first and second interconnect layers. A plurality of memory strings each extending vertically above the second interconnect layer are formed.

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of U.S. application Ser. No. 16/140,422,filed on Sep. 24, 2018, entitled “THREE-DIMENSIONAL MEMORY DEVICE HAVINGA SHIELDING LAYER AND METHOD FOR FORMING THE SAME,” which is acontinuation of International Application No. PCT/CN2018/093670, filedon Jun. 29, 2018, entitled “THREE-DIMENSIONAL MEMORY DEVICE HAVING ASHIELDING LAYER AND METHOD FOR FORMING THE SAME,” both of which arehereby incorporated by reference in their entireties.

BACKGROUND

Embodiments of the present disclosure relate to three-dimensional (3D)memory devices and fabrication methods thereof.

Planar memory cells are scaled to smaller sizes by improving processtechnology, circuit design, programming algorithm, and fabricationprocess. However, as feature sizes of the memory cells approach a lowerlimit, planar process and fabrication techniques become challenging andcostly. As a result, memory density for planar memory cells approachesan upper limit.

A 3D memory architecture can address the density limitation in planarmemory cells. The 3D memory architecture includes a memory array andperipheral devices for controlling signals to and from the memory array.

SUMMARY

Embodiments of 3D memory device having a shielding layer and fabricationmethods thereof are disclosed herein.

In one example, a 3D memory device includes a substrate, a peripheraldevice disposed on the substrate, a semiconductor layer disposed abovethe peripheral device, a plurality of memory strings each extendingvertically on the semiconductor layer, and a shielding layer disposedbetween the peripheral device and the semiconductor layer. The shieldinglayer includes a conduction region configured to receive a groundingvoltage during operation of the 3D memory device.

In another example, a 3D memory device includes a substrate, a pluralityof memory strings each extending vertically on the substrate, asemiconductor layer disposed above the plurality of memory strings, aperipheral device disposed on the semiconductor layer, and a shieldinglayer disposed between the plurality of memory strings and thesemiconductor layer. The shielding layer includes a conduction regionconfigured to receive a grounding voltage during operation of the 3Dmemory device.

In a different example, a method for forming a 3D memory device isdisclosed. A peripheral device is formed on a substrate. A firstinterconnect layer including a first plurality of interconnects isformed above the peripheral device. A shielding layer including aconduction region is formed above the first interconnect layer. A secondinterconnect layer including a second plurality of interconnects isformed above the shielding layer. The conduction region of the shieldinglayer covers an area of the first and second plurality of interconnectsin the first and second interconnect layers. A plurality of memorystrings each extending vertically above the second interconnect layerare formed.

In another example, a method for forming a 3D memory device isdisclosed. A plurality of memory strings each extending vertically on asubstrate are formed. A first interconnect layer including a firstplurality of interconnects is formed above the plurality of memorystrings. A shielding layer including a conduction region is formed abovethe first interconnect layer. A second interconnect layer including asecond plurality of interconnects is formed above the shielding layer.The conduction region of the shielding layer covers an area of the firstand second plurality of interconnects in the first and secondinterconnect layers. A peripheral device is formed above the secondinterconnect layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and form a partof the specification, illustrate embodiments of the present disclosureand, together with the description, further serve to explain theprinciples of the present disclosure and to enable a person skilled inthe pertinent art to make and use the present disclosure.

FIG. 1A illustrates a cross-section of an exemplary 3D memory devicehaving a shielding layer, according to some embodiments.

FIG. 1B illustrates a cross-section of another exemplary 3D memorydevice having a shielding layer, according to some embodiments.

FIG. 2 illustrates a plan view of an exemplary shielding layer,according to some embodiments.

FIG. 3A illustrates an exemplary layout of a shielding layer, accordingto some embodiments.

FIG. 3B illustrates another exemplary layout of a shielding layer,according to some embodiments.

FIGS. 4A-4H illustrate a fabrication process for forming an exemplary 3Dmemory device having a shielding layer, according to some embodiments.

FIG. 5 is a flowchart of a method for forming an exemplary 3D memorydevice having a shielding layer, according to some embodiments.

FIGS. 6A-6G illustrate a fabrication process for forming anotherexemplary 3D memory device having a shielding layer, according to someembodiments.

FIG. 7 is a flowchart of a method for forming another exemplary 3Dmemory device having a shielding layer, according to some embodiments.

Embodiments of the present disclosure will be described with referenceto the accompanying drawings.

DETAILED DESCRIPTION

Although specific configurations and arrangements are discussed, itshould be understood that this is done for illustrative purposes only. Aperson skilled in the pertinent art will recognize that otherconfigurations and arrangements can be used without departing from thespirit and scope of the present disclosure. It will be apparent to aperson skilled in the pertinent art that the present disclosure can alsobe employed in a variety of other applications.

It is noted that references in the specification to “one embodiment,”“an embodiment,” “an example embodiment,” “some embodiments,” etc.,indicate that the embodiment described may include a particular feature,structure, or characteristic, but every embodiment may not necessarilyinclude the particular feature, structure, or characteristic. Moreover,such phrases do not necessarily refer to the same embodiment. Further,when a particular feature, structure or characteristic is described inconnection with an embodiment, it would be within the knowledge of aperson skilled in the pertinent art to effect such feature, structure orcharacteristic in connection with other embodiments whether or notexplicitly described.

In general, terminology may be understood at least in part from usage incontext. For example, the term “one or more” as used herein, dependingat least in part upon context, may be used to describe any feature,structure, or characteristic in a singular sense or may be used todescribe combinations of features, structures or characteristics in aplural sense. Similarly, terms, such as “a,” “an,” or “the,” again, maybe understood to convey a singular usage or to convey a plural usage,depending at least in part upon context. In addition, the term “basedon” may be understood as not necessarily intended to convey an exclusiveset of factors and may, instead, allow for existence of additionalfactors not necessarily expressly described, again, depending at leastin part on context.

It should be readily understood that the meaning of “on,” “above,” and“over” in the present disclosure should be interpreted in the broadestmanner such that “on” not only means “directly on” something but alsoincludes the meaning of “on” something with an intermediate feature or alayer therebetween, and that “above” or “over” not only means themeaning of “above” or “over” something but can also include the meaningit is “above” or “over” something with no intermediate feature or layertherebetween (i.e., directly on something).

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

As used herein, the term “substrate” refers to a material onto whichsubsequent material layers are added. The substrate itself can bepatterned. Materials added on top of the substrate can be patterned orcan remain unpatterned. Furthermore, the substrate can include a widearray of semiconductor materials, such as silicon, germanium, galliumarsenide, indium phosphide, etc. Alternatively, the substrate can bemade from an electrically non-conductive material, such as a glass, aplastic, or a sapphire wafer.

As used herein, the term “layer” refers to a material portion includinga region with a thickness. A layer can extend over the entirety of anunderlying or overlying structure or may have an extent less than theextent of an underlying or overlying structure. Further, a layer can bea region of a homogeneous or inhomogeneous continuous structure that hasa thickness less than the thickness of the continuous structure. Forexample, a layer can be located between any pair of horizontal planesbetween, or at, a top surface and a bottom surface of the continuousstructure. A layer can extend horizontally, vertically, and/or along atapered surface. A substrate can be a layer, can include one or morelayers therein, and/or can have one or more layer thereupon, thereabove,and/or therebelow. A layer can include multiple layers. For example, aninterconnect layer can include one or more conductor and contact layers(in which interconnect lines and/or via contacts are formed) and one ormore dielectric layers.

As used herein, the term “nominal/nominally” refers to a desired, ortarget, value of a characteristic or parameter for a component or aprocess operation, set during the design phase of a product or aprocess, together with a range of values above and/or below the desiredvalue. The range of values can be due to slight variations inmanufacturing processes or tolerances. As used herein, the term “about”indicates the value of a given quantity that can vary based on aparticular technology node associated with the subject semiconductordevice. Based on the particular technology node, the term “about” canindicate a value of a given quantity that varies within, for example,10-30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

As used herein, the term “3D memory device” refers to a semiconductordevice with vertically oriented strings of memory cell transistors(referred to herein as “memory strings,” such as NAND memory strings) ona laterally-oriented substrate so that the memory strings extend in thevertical direction with respect to the substrate. As used herein, theterm “vertical/vertically” means nominally perpendicular to the lateralsurface of a substrate.

In some 3D memory devices, the periphery circuits and memory array arestacked to save wafer area and increase memory cell density. The stackedmemory device architecture often requires additional metal routing,which can result in extra capacitance and resistance. Subsequently, whenthe noise factor increases, signals can be distorted and therefore, failin signal integrity during transmission. Moreover, coupling effectbetween periphery circuits and memory array becomes a serious problem astheir metal interconnects are much closer in a stacked memory devicearchitecture than in a non-stacked architecture, thereby exacerbatingsignal distortion during memory operation.

Various embodiments in accordance with the present disclosure provide a3D memory device having a shielding layer between the stacked peripherycircuits and memory array with a grounding voltage applied on it duringthe memory operation. The grounding voltage applied to the conductivematerials (e.g., metal, metal alloy, metal silicide, and/or dopedsemiconductor) in the shielding layer can shield the transfer ofelectrical energy between metal interconnects or any other circuitsegments and thus, reduce or even avoid the coupling effect between thestacked periphery circuits and memory array in a 3D memory device duringits operation.

FIG. 1A illustrates a cross-section of an exemplary 3D memory device 100having a shielding layer 102 according to some embodiments of thepresent disclosure. 3D memory device 100 represents an example of amonolithic 3D memory device. The term “monolithic” means that thecomponents of 3D memory device 100 are formed on a single substrate. 3Dmemory device 100 can include a substrate 104, which can include silicon(e.g., single crystalline silicon), silicon germanium (SiGe), galliumarsenide (GaAs), germanium (Ge), silicon on insulator (SOI), or anyother suitable materials.

3D memory device 100 can include a peripheral device on substrate 104.The peripheral device can be formed “on” substrate 104, in which theentirety or part of the peripheral device is formed in substrate 104(e.g., below the top surface of substrate 104) and/or directly onsubstrate 104. The peripheral device can include a plurality oftransistors 106 formed on substrate 104. Isolation regions 108 and dopedregions (e.g., source regions and drain regions of transistors 106) canbe formed in substrate 104 as well.

In some embodiments, the peripheral device can include any suitabledigital, analog, and/or mixed-signal peripheral circuits used forfacilitating the operation of 3D memory device 100. For example, theperipheral device can include one or more of a page buffer, a decoder(e.g., a row decoder and a column decoder), a sense amplifier, a driver,a charge pump, a current or voltage reference, or any active or passivecomponents of the circuits (e.g., transistors, diodes, resistors, orcapacitors). In some embodiments, the peripheral device is formed onsubstrate 104 using complementary metal-oxide-semiconductor (CMOS)technology (also known as a “CMOS chip”).

3D memory device 100 can include an interconnect layer 110 abovetransistors 106 (referred to herein as a “peripheral interconnectlayer”) to transfer electrical signals to and from transistors 106.Peripheral interconnect layer 110 can include a plurality ofinterconnects (also referred to herein as “contacts”), including lateralinterconnect lines 112 and vertical interconnect access (via) contacts114. As used herein, the term “interconnects” can broadly include anysuitable types of interconnects, such as middle-end-of-line (MEOL)interconnects and back-end-of-line (BEOL) interconnects. Peripheralinterconnect layer 110 can further include one or more interlayerdielectric (ILD) layers (also known as “intermetal dielectric (IMD)layers”) in which interconnect lines 112 and via contacts 114 can form.That is, peripheral interconnect layer 110 can include interconnectlines 112 and via contacts 114 in multiple ILD layers. Interconnectlines 112 and via contacts 114 in peripheral interconnect layer 110 caninclude conductor materials including, but not limited to, tungsten (W),cobalt (Co), copper (Cu), aluminum (Al), silicides, or any combinationthereof. The ILD layers in peripheral interconnect layer 110 can includedielectric materials including, but not limited to, silicon oxide,silicon nitride, silicon oxynitride, low dielectric constant (low-k)dielectrics, or any combination thereof.

3D memory device 100 can include a memory array device above theperipheral device. It is noted that x and y axes are added in FIG. 1A tofurther illustrate the spatial relationship of the components in 3Dmemory device 100. Substrate 104 includes two lateral surfaces (e.g., atop surface and a bottom surface) extending laterally in the x-direction(the lateral direction or width direction). As used herein, whether onecomponent (e.g., a layer or a device) is “on,” “above,” or “below”another component (e.g., a layer or a device) of a semiconductor device(e.g., 3D memory device 100) is determined relative to the substrate ofthe semiconductor device (e.g., substrate 104) in the y-direction (thevertical direction or thickness direction) when the substrate ispositioned in the lowest plane of the semiconductor device in they-direction. The same notion for describing spatial relationship isapplied throughout the present disclosure.

In some embodiments, 3D memory device 100 is a NAND Flash memory devicein which memory cells are provided in the form of an array of NANDmemory strings 116 each extending vertically on a semiconductor layer118 disposed above the peripheral device (e.g., transistors 106).Semiconductor layer 118 can include polycrystalline silicon(polysilicon) or amorphous silicon deposited by, for example, physicalvapor deposition (PVD), chemical vapor deposition (CVD), or atomic layerdeposition (ALD). Semiconductor layer 118 can be doped to form dopedregions in which source regions of NAND memory strings 116 can beformed. It is understood that in FIG. 1A, as 3D memory device 100 is amonolithic 3D memory device in which the memory array device is disposedabove the peripheral device, NAND memory strings 116 are formed directlyon deposited semiconductor layer 118, as opposed to substrate 104 (e.g.,a single crystalline silicon).

The memory array device can include NAND memory strings 116 that extendvertically through a plurality of pairs each including a conductor layer120 and a dielectric layer 122 (referred to herein as“conductor/dielectric layer pairs”). The stacked conductor/dielectriclayer pairs are also referred to herein as an “alternatingconductor/dielectric stack” 124. Alternating conductor/ dielectric stack124 can be formed on semiconductor layer 118. Conductor layers 120 anddielectric layers 122 in alternating conductor/ dielectric stack 124alternate in the vertical direction. In other words, except the ones atthe top or bottom of alternating conductor/ dielectric stack 124, eachconductor layer 120 can be adjoined by two dielectric layers 122 on bothsides, and each dielectric layer 122 can be adjoined by two conductorlayers 120 on both sides. Conductor layers 120 can each have the samethickness or different thicknesses. Similarly, dielectric layers 122 caneach have the same thickness or different thicknesses. Conductor layers120 can include conductor materials including, but not limited to, W,Co, Cu, Al, doped silicon, silicides, or any combination thereof.Dielectric layers 122 can include dielectric materials including, butnot limited to, silicon oxide, silicon nitride, silicon oxynitride, orany combination thereof.

As shown in FIG. 1A, each NAND memory string 116 can include asemiconductor channel 126 and a dielectric layer 128 (also known as a“memory film”). In some embodiments, semiconductor channel 126 includessilicon, such as amorphous silicon, polysilicon, or single crystallinesilicon. In some embodiments, dielectric layer 128 is a composite layerincluding a tunneling layer, a storage layer (also known as “chargetrap/storage layer”), and a blocking layer. Each NAND memory string 116can have a cylinder shape (e.g., a pillar shape). Semiconductor channel126, the tunneling layer, the storage layer, and the blocking layer arearranged along a direction from the center toward the outer surface ofthe pillar in this order, according to some embodiments. The tunnelinglayer can include silicon oxide, silicon oxynitride, or any combinationthereof. The storage layer can include silicon nitride, siliconoxynitride, silicon, or any combination thereof. The blocking layer caninclude silicon oxide, silicon oxynitride, high dielectric constant(high-k) dielectrics, or any combination thereof. In one example, theblocking layer can include a composite layer of silicon oxide/siliconoxynitride/silicon oxide (ONO). In another example, the blocking layercan include a high-k dielectric layer, such as an aluminum oxide(Al₂O₃), or hafnium oxide (HfO₂) or tantalum oxide (Ta₂O₅) layer, and soon.

In some embodiments, the memory array device further includes a gateline slit (GLS) 130 that extends vertically through alternatingconductor/dielectric stack 124. GLS 130 can be used to form theconductor/dielectric layer pairs in alternating conductor/dielectricstack 124 by a gate replacement process. In some embodiments, GLS 130 isfirstly filled with dielectric materials, for example, silicon oxide,silicon nitride, or any combination thereof, for separating the NANDmemory string array into different regions (e.g., memory fingers and/ormemory blocks). Then, GLS 130 is filled with conductive and/orsemiconductor materials, for example, W, Co, polysilicon, or anycombination thereof, for electrically controlling an array common source(ACS).

In some embodiments, the memory array device further includes word linevia contacts 132 in a staircase structure region of alternatingconductor/dielectric stack 124. Word line via contacts 132 can extendvertically within a dielectric layer. Each word line via contact 132 canhave its lower end in contact with corresponding conductor layer 120 inalternating conductor/dielectric stack 124 to individually address acorresponding word line of the memory array device. As used herein, the“upper end” of a component (e.g., word line via contact 132) is the endfarther away from substrate 104 in the y-direction, and the “lower end”of the component is the end closer to substrate 104 in the y-direction.Word line via contacts 132 can be contact holes and/or contact trenchesfilled with a conductor (e.g., W). In some embodiments, the contactholes and/or contact trenches are also filled with a barrier layer, anadhesion glue layer, and/or a seed layer besides the conductor.

Similar to the peripheral device, the memory array device of 3D memorydevice 100 can also include interconnect layers for transferringelectrical signals to and from NAND memory strings 116. As shown in FIG.1A, 3D memory device 100 can include an interconnect layer 134 (referredto herein as a “lower array interconnect layer”) below NAND memorystrings 116 and semiconductor layer 118 and an interconnect layer 136(referred to herein as an “upper array interconnect layer”) above NANDmemory strings 116 and semiconductor layer 118.

Upper array interconnect layer 136 can be formed above alternatingconductor/dielectric stack 124 and include a plurality of interconnects,including interconnect lines 138 and via contacts 140 in one or more ILDlayers. In some embodiments, the interconnects in upper arrayinterconnect layer 136 include bit lines and bit line contacts each incontact with the upper end of corresponding NAND memory string 116 toindividually address corresponding NAND memory string 116. In someembodiments, the interconnects in upper array interconnect layer 136also include source lines in contact with the array common sources ofNAND memory strings 116. In some embodiments, upper array interconnectlayer 136 further includes any other suitable BEOL interconnects thatcan transfer electrical signals between 3D memory device 100 andperipheral circuits. Interconnect lines 138 and via contacts 140 inupper array interconnect layer 136 can include conductor materialsincluding, but not limited to, W, Co, Cu, Al, silicides, or anycombination thereof. The ILD layers in upper array interconnect layer136 can include dielectric materials including, but not limited to,silicon oxide, silicon nitride, silicon oxynitride, low-k dielectrics,or any combination thereof.

Lower array interconnect layer 134 can include a plurality ofinterconnects, including interconnect lines 142 and via contacts 144 inone or more ILD layers. In some embodiments, the interconnects in lowerarray interconnect layer 134 include via contacts 144 each in contactwith the lower end of corresponding NAND memory string 116 and extendingvertically through semiconductor layer 118. In some embodiments, theinterconnects in lower array interconnect layer 134 are used forbackside metal routing of the memory array device.

In some embodiments, the memory array device further includes one ormore through array contacts (TACs) 146 that extend vertically throughalternating conductor/dielectric stack 124 and semiconductor layer 118.The upper end of TAC 146 can contact an interconnect in upper arrayinterconnect layer 136, and the lower end of TAC 146 can contact anotherinterconnect in lower array interconnect layer 134. TAC 146 can thusmake an electrical connection between peripheral interconnect layer 110and upper array interconnect layer 136 and carry electrical signals fromthe peripheral device to a BEOL interconnect of the memory array device.

During the operation of 3D memory device 100 (when 3D memory device 100is in use, for example, performing cell read, write/program, erase,setting, boosting, etc.), coupling effect between the interconnects inperipheral interconnect layer 110 and lower array interconnect layer 134can cause signal distortion. To address this problem, as shown in FIG.1A, 3D memory device 100 includes shielding layer 102 betweentransistors 106 and semiconductor layer 118. In some embodiments,shielding layer 102 is formed between peripheral interconnect layer 110and lower array interconnect layer 134 to reduce the coupling effectbetween the interconnects in the adjacent interconnect layers during theoperation of 3D memory device 100. As shown in FIG. 1A, peripheralinterconnect layer 110 is disposed between transistors 106 and shieldinglayer 102, and lower array interconnect layer 134 is disposed betweenNAND memory strings 116 and shielding layer 102.

Shielding layer 102 can include one or more conduction regions 148 andone or more isolation regions 150. Conduction region 148 can includeconductive materials that have a higher electrical conductivity than anundoped semiconductor material, such as undoped silicon (e.g., amorphoussilicon, single crystalline silicon, or polysilicon). In someembodiments, conduction region 148 has an electrical conductivity of atleast about 1×10⁴ S/m at about 20° C., such as at least 1×10⁴ S/m at 20°C. In some embodiments, conduction region 148 has an electricalconductivity of between about 1×10⁴ S/m and about 1×10⁸ S/m at about 20°C., such as between 1×10⁴ S/m and 1×10⁸ S/m at 20° C. (e.g., 1×10⁴ S/m,1×10⁵ S/m, 5×10⁵ S/m, 1×10⁶ S/m, 2×10⁶ S/m, 3×10⁶ S/m, 4×10⁶ S/m, 5×10⁶S/m, 6×10⁶ S/m, 7×10⁶ S/m, 8×10⁶ S/m, 9×10⁶ S/m, 1×10⁷ S/m, 2×10⁷ S/m,3×10⁷ S/m, 4×10⁷ S/m, 5×10⁷ S/m, 6×10⁷ S/m, 7×10⁷ S/m, 8×10⁷ S/m, 9×10⁷S/m, 1×10⁸ S/m, any range bounded by the lower end by any of thesevalues, or in any range defined by any two of these values, at 20° C.).The conductive materials in conduction region 148 can include, but arenot limited to, metals, metal alloys, metal silicides, and dopedsemiconductors. In some embodiments, conduction region 148 includes oneor more metals, such as W, Cu, Co, Al, nickel (Ni), and titanium (Ti).Conduction region 148 can also include any other suitable metals, suchas silver (Ag), gold (Au), platinum (Pt), ruthenium (Ru), etc. In someembodiments, conduction region 148 includes one or more metal alloys,each of which is an alloy of at least two of Cu, Co, Ni, Ti, and W(e.g., TiNi alloy or a combination of TiNi alloy and TiW alloy), or anyother suitable metal alloys of, for example, Ag, Al, Au, Pt, iron (Fe),chromium (Cr), etc. In some embodiments, conduction region 148 includesone or more metal silicides, such as copper silicide, cobalt silicide,nickel silicide, titanium silicide, and tungsten silicide. Conductionregion 148 can also include any other suitable metal silicides, such assilver silicide, aluminum silicide, gold silicide, platinum silicide,etc. In some embodiments, conduction region 148 includes a semiconductormaterial doped with a dopant at a concentration such that the electricalconductivity of conduction region 148 is increased into the rangesdescribed above.

In some embodiments, shielding layer 102 has a thickness between about 1nm and about 1 μm, such as between 1 nm and 1 μm (e.g., 1 nm, 2 nm, 3nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm,350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm,800 nm, 850 nm, 900 nm, 950 nm, 1 μm, any range bounded by the lower endby any of these values, or in any range defined by any two of thesevalues). In some embodiments, shielding layer 102 has a thicknessbetween about 1 μm and about 20 μm, such as between 1 μm and 20 μm(e.g., 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, anyrange bounded by the lower end by any of these values, or in any rangedefined by any two of these values). In some embodiments, shieldinglayer 102 is a compound layer having a plurality of films, such as oneor more conductive films and dielectric films. The thickness rangesdescribed above may refer to the total thickness of a compound shieldinglayer or the thickness of the conductive film(s) in a compound shieldinglayer.

Shielding layer 102 can be patterned to form any suitable layout withdifferent numbers of conduction regions 148 and isolation regions 150 indifferent arrangements. As shown in FIG. 1A, in order to electricallyconnect the stacked memory array device (e.g., NAND memory strings 116)and the peripheral device (e.g., transistors 106) on different planes of3D memory device 100, interconnects are formed between peripheralinterconnect layer 110 and array interconnect layers 134 and 136. As aresult, 3D memory device 100 can include via contacts 152 extendingvertically through shielding layer 102. Via contact 152 can be incontact with the interconnects in peripheral interconnect layer 110 andthe interconnects in lower array interconnect layer 134. Via contact 152can also be in contact with the interconnects in peripheral interconnectlayer 110 and TAC 146 to make an electrical connection with theinterconnects in upper array interconnect layer 136.

In some embodiments, isolation region 150 extends across the entirethickness of shielding layer 102 to electrically isolate conductionregion 148 and via contacts 152. Isolation region 150 can includedielectric materials including, but not limited to, silicon oxide,silicon nitride, silicon oxynitride, doped silicon oxide, any othersuitable dielectric materials, or any combination thereof. Patterningprocess (e.g., photolithography and dry/wet etch) can be used forpatterning isolation region 150 in shielding layer 102. Isolation region150 then can be formed by thermal growth and/or thin film deposition ofthe dielectric materials in the patterned region.

For example, FIG. 2 illustrates a plan view of an exemplary shieldinglayer 202, according to some embodiments. As shown in FIG. 2, shieldinglayer 202 includes a conduction region 204 and isolation regions 206 forelectrically isolating conduction region 204 and via contacts 208extending through shielding layer 202. Conduction region 204 can coversubstantially the entire area of a substrate 200 except for the areasoccupied by isolation regions 206 and via contacts 208.

In addition to accommodating via contacts 152 through shielding layer102, the layout of shielding layer 102 can vary with respect to the areait covers. For example. FIGS. 3A-3B illustrate exemplary layouts ofshielding layers 302 and 310, according to various embodiments. As shownin FIG. 3A, interconnects 306 and 308 in adjacent interconnect layersare separated vertically by shielding layer 302. A conduction region 304of shielding layer 302 covers substantially the entire area of asubstrate 300 (except for the areas occupied by the isolation regionsand via contacts, not shown) regardless of the layout of interconnects306 and 308. As shown in FIG. 3B, a conduction region 312 of shieldinglayer 310 does not cover substantially the entire area of substrate 300,but instead, covers the area of interconnects 306 and interconnects 308in the adjacent interconnect layers separated by shielding layer 310(e.g., peripheral interconnect layer 110 and lower array interconnectlayer 134 in FIG. 1A). It is understood that the layout of a shieldinglayer is not limited to the examples illustrated above and can vary indifferent embodiments as long as its conduction region covers at leastthe area of interconnects in the adjacent interconnect layers separatedby the shielding layer.

Referring back to FIG. 1A, conduction region 148 of shielding layer 102is configured to receive a grounding voltage during the operation of 3Dmemory device 100. Conduction region 148 can be electrically connectedto a voltage source 154 (or ground) during the operation of 3D memorydevice 100. In some embodiments, the grounding voltage is between about0.1 V and about 50 V, such as between 0.1 V and 50 V (e.g., 0.1 V, 0.2V, 0.3 V, 0.4 V, 0.5 V, 0.6 V, 0.7 V, 0.8 V, 0.9 V, 1 V, 2 V, 3 V, 4 V,5 V, 6 V, 7 V, 8 V, 9 V, 10 V, 15 V, 20 V, 25 V, 30 V, 35 V, 40 V, 45 V,50 V, any range bounded by the lower end by any of these values, or inany range defined by any two of these values). It is understood that thegrounding voltage can be adjusted based on various attributes ofshielding layer 102, such as the thickness and electrical conductivity.During the operation of 3D memory device 100, the grounding voltageapplied to conduction region 148 of shielding layer 102 can reduce (oravoid) the coupling effect between the interconnects in peripheralinterconnect layer 110 and lower array interconnect layer 134.

FIG. 1B illustrates a cross-section of another exemplary 3D memorydevice 101 having a shielding layer 103, according to some embodimentsof the present disclosure. Similar to 3D memory device 100 describedabove in FIG. 1A, 3D memory device 101 represents an example of amonolithic 3D memory device in which a peripheral device and a memoryarray device are stacked and separated by shielding layer 103. Differentfrom 3D memory device 100 described above in FIG. 1A in which theperipheral device is below the memory array device, 3D memory device 101in FIG. 1B includes a peripheral device disposed above a memory arraydevice. It is understood that the details of similar structures (e.g.,materials, fabrication process, functions, etc.) in both 3D memorydevices 100 and 101 may not be repeated below.

3D memory device 101 can include a memory array device on a substrate105. In some embodiments, an array of NAND memory strings 107 eachextends vertically through an alternating conductor/ dielectric stack109 on substrate 105. Alternating conductor/dielectric stack 109 caninclude a plurality of pairs each including a conductor layer 111 and adielectric layer 113. As shown in FIG. 1B, each NAND memory string 107can include a semiconductor channel 115 and a dielectric layer 117 (alsoknown as a “memory film”).

In some embodiments, the memory array device further includes a GLS 119that extends vertically through alternating conductor/dielectric stack109. GLS 119 can be used to form the conductor/dielectric layer pairs inalternating conductor/dielectric stack 109 by a gate replacementprocess. In some embodiments, GLS 119 is firstly filled with dielectricmaterials, for example, silicon oxide, silicon nitride, or anycombination thereof, for separating the NAND memory string array intodifferent regions (e.g., memory fingers and/or memory blocks). In someembodiments, the memory array device further includes word line viacontacts 121 in a staircase structure region of alternatingconductor/dielectric stack 109. Word line via contacts 121 can extendvertically within a dielectric layer. Each word line via contact 121 canhave its lower end in contact with corresponding conductor layer 111 inalternating conductor/ dielectric stack 109 to individually address acorresponding word line of the memory array device.

3D memory device 101 can include an interconnect layer 123 above NANDmemory strings 107 (referred to herein as an “array interconnect layer”)to transfer electrical signals to and from NAND memory strings 107.Array interconnect layer 123 can include a plurality of interconnects,including interconnect lines 125 and via contacts 127. In someembodiments, the interconnects in array interconnect layer 123 includebit lines and bit line contacts each in contact with the upper end ofcorresponding NAND memory string 107 to individually addresscorresponding NAND memory string 107. In some embodiments, theinterconnects in array interconnect layer 123 also include source linesin contact with the array common sources of NAND memory strings 107. Insome embodiments, array interconnect layer 123 further includes anyother suitable BEOL interconnects that can transfer electrical signalsbetween the stacked memory array device and peripheral device.

3D memory device 101 can include a peripheral device formed on asemiconductor layer 129 disposed above the memory array device (e.g.,NAND memory strings 107). Semiconductor layer 129 can includepolysilicon or amorphous silicon. It is understood that in FIG. 1B, as3D memory device 101 is a monolithic 3D memory device in which theperipheral device is disposed above the memory array device, theperipheral device (e.g., transistors 131) is formed directly ondeposited semiconductor layer 129, as opposed to substrate 105 (e.g., asingle crystalline silicon). Isolation regions 133 and doped regions(e.g., source regions and drain regions of transistors 131) can beformed in semiconductor layer 129 as well. In some embodiments, theperipheral device can include any suitable digital, analog, and/ormixed-signal peripheral circuits used for facilitating the operation of3D memory device 101.

Similar to the memory array device, the peripheral device of 3D memorydevice 101 can also include interconnect layers for transferringelectrical signals to and from transistors 131. As shown in FIG. 1B, 3Dmemory device 101 can include an interconnect layer 135 (referred toherein as a “lower peripheral interconnect layer”) below transistors 131and semiconductor layer 129 and an interconnect layer 137 (referred toherein as an “upper peripheral interconnect layer”) above transistors131 and semiconductor layer 129.

Upper peripheral interconnect layer 137 can be formed above transistors131 and include a plurality of interconnects, including interconnectlines 139 and via contacts 141 in one or more ILD layers. In someembodiments, upper peripheral interconnect layer 137 includes anysuitable BEOL interconnects that can transfer electrical signals between3D memory device 101 and peripheral circuits. Lower peripheralinterconnect layer 135 can include a plurality of interconnects,including interconnect lines 143 and via contacts 145 in one or more ILDlayers. In some embodiments, the interconnects in lower peripheralinterconnect layer 135 include via contacts 145 extending verticallythrough semiconductor layer 129. In some embodiments, the interconnectsin lower peripheral interconnect layer 135 are used for backside metalrouting of the peripheral device (e.g., transistors 131).

During the operation of 3D memory device 101 (when 3D memory device 101is in use, for example, performing cell read, write/program, erase,setting, boosting, etc.), coupling effect between the interconnects inarray interconnect layer 123 and lower peripheral interconnect layer 135can cause signal distortion. To address this problem, as shown in FIG.1B, 3D memory device 101 includes shielding layer 103 between NANDmemory strings 107 and semiconductor layer 129. In some embodiments,shielding layer 103 is formed between array interconnect layer 123 andlower peripheral interconnect layer 135 to reduce the coupling effectbetween the interconnects in the adjacent interconnect layers during theoperation of 3D memory device 101. As shown in FIG. 1B, arrayinterconnect layer 123 is disposed between NAND memory strings 107 andshielding layer 103, and lower peripheral interconnect layer 135 isdisposed between transistors 131 and shielding layer 103.

Shielding layer 103 can include one or more conduction regions 147 andone or more isolation regions 149. Shielding layer 103 can be patternedto form any suitable layout with different numbers of conduction regions147 and isolation regions 149 in different arrangements. As shown inFIG. 1B, in order to electrically connect the stacked memory arraydevice (e.g., NAND memory strings 107) and the peripheral device (e.g.,transistors 131) on different planes of 3D memory device 101,interconnects are formed between array interconnect layer 123 andperipheral interconnect layers 135 and 137. As a result, 3D memorydevice 101 can include via contacts 151 extending vertically throughshielding layer 103. Via contact 151 can be in contact with theinterconnects in array interconnect layer 123 and the interconnects inlower peripheral interconnect layer 135. In some embodiments, isolationregion 149 extends across the entire thickness of shielding layer 103 toelectrically isolate conduction region 147 and via contacts 151.

In some embodiments, conduction region 147 of shielding layer 103 isconfigured to receive a grounding voltage during the operation of 3Dmemory device 101. Conduction region 147 can be electrically connectedto a voltage source 153 (or ground) during the operation of 3D memorydevice 101. It is understood that the grounding voltage can be adjustedbased on various attributes of shielding layer 103, such as thethickness and electrical conductivity. During the operation of 3D memorydevice 101, the grounding voltage applied to conduction region 147 ofshielding layer 103 can reduce (or avoid) the coupling effect betweenthe interconnects in array interconnect layer 123 and lower peripheralinterconnect layer 135. It is understood that other attributes ofshielding layer 103 (and its conduction region 147 and isolation region149) can be similar to those described above with respect to shieldinglayer 102 in FIGS. 1A, 2, and 3A-3B.

FIGS. 4A-4H illustrate a fabrication process for forming an exemplary 3Dmemory device having a shielding layer, according to some embodiments ofthe present disclosure. FIG. 5 is a flowchart of a method 500 forforming an exemplary 3D memory device having a shielding layer,according to some embodiments. Examples of the 3D memory device depictedin FIGS. 4A-4H and FIG. 5 include 3D memory device 100 depicted in FIG.1A. FIGS. 4A-4H and FIG. 5 will be described together. It is understoodthat the operations shown in method 500 are not exhaustive and thatother operations can be performed as well before, after, or between anyof the illustrated operations. Further, some of the operations may beperformed simultaneously, or in a different order than shown in FIG. 5.

Referring to FIG. 5, method 500 starts at operation 502, in which aperipheral device is formed on a substrate. The substrate can be asilicon substrate. As illustrated in FIG. 4A, a peripheral device isformed on a silicon substrate 402. The peripheral device can include aplurality of transistors 404 formed on silicon substrate 402.Transistors 404 can be formed by a plurality of processes including, butnot limited to, photolithography, dry/wet etch, thin film deposition,thermal growth, implantation, chemical mechanical polishing (CMP), andany other suitable processes. In some embodiments, doped regions areformed in silicon substrate 402, which function, for example, as sourceregions and/or drain regions of transistors 404. In some embodiments,isolation regions 406 (e.g., shallow trench isolations (STIs)) are alsoformed in silicon substrate 402 by wet/dry etch and thin filmdeposition.

Method 500 proceeds to operation 504, as illustrated in FIG. 5, in whicha first interconnect layer (e.g., a peripheral interconnect layer) isformed above the peripheral device. The first interconnect layer caninclude a first plurality of interconnects in one or more ILD layers. Asillustrated in FIG. 4B, a peripheral interconnect layer 408 can beformed on silicon substrate 402 and above transistors 404. Peripheralinterconnect layer 408 can include interconnects, including interconnectlines 410 and via contacts 412 of MEOL and/or BEOL in a plurality of ILDlayers, to make electrical connections with the peripheral device (e.g.,transistors 404).

In some embodiments, peripheral interconnect layer 408 includes multipleILD layers and interconnects therein formed in multiple processes. Forexample, interconnect lines 410 and via contacts 412 can includeconductor materials deposited by one or more thin film depositionprocesses including, but not limited to, CVD, PVD, ALD, electroplating,electroless plating, or any combination thereof. Fabrication processesto form interconnect lines 410 and via contacts 412 can also includephotolithography, CMP, wet/dry etch, or any other suitable processes.The ILD layers can include dielectric materials deposited by one or morethin film deposition processes including, but not limited to, CVD, PVD,ALD, or any combination thereof. The ILD layers and interconnectsillustrated in FIG. 4B can be collectively referred to as an“interconnect layer” (e.g., peripheral interconnect layer 408).

Method 500 proceeds to operation 506, as illustrated in FIG. 5, in whicha shielding layer is formed above the first interconnect layer (e.g.,the peripheral interconnect layer). Operation 506 can include forming aconduction region and an isolation region above the first interconnectlayer. The conduction region can cover the area of the interconnects inthe first interconnect layer. In some embodiments, the conduction regionof the shielding layer covers substantially the area of the substrate.Method 500 can further include additional operation(s) to form a contact(e.g., via contact) extending vertically through the shielding layer andin contact with the interconnects of the first interconnect layer. Thecontact can be electrically isolated from the conduction region in theshielding layer by the isolation region.

As illustrated in FIG. 4C, a conductive film 414 can be formed on thetop surface of peripheral interconnect layer 408. The conductivematerials in conductive film 414 can include, but not limited to,metals, metal alloys, metal silicides, and doped semiconductors. In someembodiments, conductive film 414 includes one or more metals, such asCu, Co, Ni, Ti, W, or any other suitable metals. In some embodiments,conductive film 414 includes one or more metal alloys, each of which isan alloy of at least two of Cu, Co, Ni, Ti, W (e.g., TiNi alloy or acombination of TiNi alloy and TiW alloy), or any other suitable metalalloys. In some embodiments, conductive film 414 includes one or moremetal silicides, such as copper silicide, cobalt silicide, nickelsilicide, titanium silicide, tungsten silicide, or any other suitablemetal silicides. In some embodiments, conductive film 414 includes oneor more doped semiconductors, such as doped polysilicon, doped amorphoussilicon, or any other suitable doped semiconductors.

Conductive film 414 can be formed by one or more thin film depositionprocesses including, but not limited to, CVD, PVD, ALD, electroplating,electroless plating, or any combination thereof. Depending on theconductive materials in conductive film 414, the deposition ofconductive film 414 may involve multiple processes. In some embodiments,the deposition of a metal silicide conductive film involves depositionof a silicon film, deposition of a metal film, and silicidation of thesilicon and metal films by a thermal treatment (e.g., annealing,sintering, or any other suitable process). In some embodiments, thedeposition of a doped semiconductor conductive film involves depositionof a semiconductor film and doping of the semiconductor film withdopants by ion implantation and/or thermal diffusion.

In some embodiments, deposited conductive film 414 has a thicknessbetween about 1 nm and about 1 μm, such as between 1 nm and 1 μm (e.g.,1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 20 nm, 30nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 150 nm, 200 nm,250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm,700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm, 1 μm, any range boundedby the lower end by any of these values, or in any range defined by anytwo of these values). In some embodiments, deposited conductive film 414has a thickness between about 1 μm and about 20 μm, such as between 1 μmand about 20 μm (e.g., 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19μm, 20 μm, any range bounded by the lower end by any of these values, orin any range defined by any two of these values).

As illustrated in FIG. 4C, a dielectric film 416 can be formed onconductive film 414. Dielectric film 416 can include dielectricmaterials including, but not limited to, silicon oxide, silicon nitride,silicon oxynitride, low-k dielectrics, or any combination thereof.Dielectric film 416 can be formed by thermal growth and/or one or morethin film deposition processes including, but not limited to, CVD, PVD,ALD, or any combination thereof.

As illustrated in FIG. 4D, conductive film 414 can be patterned to forma shielding layer 418 having a conduction region 420 and one or moreisolation regions 422. In some embodiments, conductive film 414 ispatterned to form isolation regions 422, and the remaining conductivematerials in conductive film 414 become conduction region 420.Conduction region 420 and isolation regions 422 can be collectivelyreferred to herein as shielding layer 418. Isolation region 422 caninclude dielectric materials including, but not limited to, siliconoxide, silicon nitride, silicon oxynitride, doped silicon oxide, anyother suitable dielectric materials, or any combination thereof.Patterning process (e.g., photolithography and dry/wet etch) can be usedfor patterning isolation regions 422 in shielding layer 418. Isolationregions 422 can then be formed by thermal growth and/or thin filmdeposition of dielectric materials in the patterned region. Shieldinglayer 418 can be patterned to form any suitable layout in differentarrangements as described above with respect to FIG. 2 and FIGS. 3A-3B.

As illustrated in FIG. 4D, one or more via contacts 424 can be formedthrough dielectric film 416 and shielding layer 418 and in contact withinterconnects 410 and 412 in peripheral interconnect layer 408. Viacontacts 424 can be electrically isolated from conduction region 420 ofshielding layer 418 by isolation regions 422. In some embodiments, viacontacts 424 are formed by first patterning via holes through dielectricfilm 416 and shielding layer 418 using patterning process (e.g.,photolithography and dry/wet etch of dielectric materials in dielectricfilm 416 and conductive materials in shielding layer 418). The via holescan be filled with a conductor (e.g., W). In some embodiments, fillingthe via holes includes depositing a barrier layer, an adhesion layer,and/or a seed layer before depositing the conductor.

Method 500 proceeds to operation 508, as illustrated in FIG. 5, in whicha second interconnect layer (e.g., a lower array interconnect layer) isformed above the shielding layer. The second interconnect layer caninclude a second plurality of interconnects in one or more ILD layers.The conduction region of the shielding layer formed at operation 506 cancover the area of the interconnects in the second interconnect layer aswell. That is, the conduction region of the shielding layer can coverthe area of both the first and second interconnects in the first andsecond interconnect layers. A semiconductor layer (e.g., a siliconlayer) can be formed above the second interconnect layer.

As illustrated in FIG. 4E, a lower array interconnect layer 426 can beformed above shielding layer 418. Lower array interconnect layer 426 caninclude interconnects, including interconnect lines 428 and via contacts430 in one or more ILD layers for backside metal routing.

In some embodiments, lower array interconnect layer 426 includesmultiple ILD layers (e.g., including dielectric film 416 in FIG. 4D) andinterconnects therein formed in multiple processes. For example,interconnect lines 428 and via contacts 430 can include conductormaterials deposited by one or more thin film deposition processesincluding, but not limited to, CVD, PVD, ALD, electroplating,electroless plating, or any combination thereof. Fabrication processesto form interconnect lines 428 and via contacts 430 can also includephotolithography, CMP, wet/dry etch, or any other suitable processes.The ILD layers can include dielectric materials deposited by one or morethin film deposition processes including, but not limited to, CVD, PVD,ALD, or any combination thereof. The ILD layers and interconnectsillustrated in FIG. 4E as well as dielectric film 416 illustrated inFIG. 4D can be collectively referred to as an “interconnect layer”(e.g., lower array interconnect layer 426).

As illustrated in FIG. 4E, a silicon layer 432 can be formed above lowerarray interconnect layer 426. Silicon layer 432 can include polysiliconor amorphous silicon deposited by one or more thin film depositionprocesses including, but not limited to, CVD, PVD, ALD, or anycombination thereof. Doped regions (e.g., wells) in silicon layer 432can be formed by ion implantation and/or thermal diffusion of dopants atdesired doping concentrations. Isolation regions (e.g., STIs) can alsobe formed in silicon layer 432 by wet/dry etch and thin film deposition.

Method 500 proceeds to operation 510, as illustrated in FIG. 5, in whicha plurality of memory strings each extending vertically above the secondinterconnect layer (and the semiconductor layer) are formed. To form thememory strings, an alternating conductor/dielectric stack can be formedon the semiconductor layer, and each memory string can be formed toextend vertically through the alternating conductor/dielectric stack. Athird interconnect layer (e.g., an upper array interconnect layer) canbe formed above the alternating conductor/dielectric stack. In someembodiments, a contact (e.g., a TAC) extending vertically through thealternating conductor/dielectric stack and the semiconductor layer isformed and in contact with the second interconnect layer (e.g., thelower array interconnect layer), so that the first interconnect layer(e.g., the peripheral interconnect layer) is electrically connected tothe third interconnect layer (e.g., the upper array interconnect layer).

As illustrated in FIG. 4F, pairs of first dielectric layer 434 andsecond dielectric layer 436 (referred to herein as “dielectric layerpairs”) are formed on silicon layer 432. The stacked dielectric layerpairs can form an alternating dielectric stack 438. Alternatingdielectric stack 438 can include an alternating stack of firstdielectric layer 434 and second dielectric layer 436 that is differentfrom first dielectric layer 434. In some embodiments, each dielectriclayer pair includes a layer of silicon nitride and a layer of siliconoxide. In some embodiments, first dielectric layers 434 can each havethe same thickness or have different thicknesses. Similarly, seconddielectric layers 436 can each have the same thickness or have differentthicknesses. Alternating dielectric stack 438 can be formed by one ormore thin film deposition processes including, but not limited to, CVD,PVD, ALD, or any combination thereof. In some embodiments, alternatingdielectric stack 438 can be replaced by a plurality of conductor/dielectric layer pairs, i.e., an alternating stack of a conductor layer(e.g., polysilicon) and a dielectric layer (e.g., silicon oxide).

As illustrated in FIG. 4G, NAND memory strings 440 are formed abovesilicon layer 432. Each first dielectric layer 434 of alternatingdielectric stack 438 can be replaced by a conductor layer 442, therebyforming a plurality of conductor/dielectric layer pairs in analternating conductor/dielectric stack 444. The replacement of firstdielectric layers 434 with conductor layers 442 can be performed bywet/dry etch of first dielectric layers 434 selective to seconddielectric layers 436 and filling the structure with conductor layers442. Conductor layers 442 can include conductor materials including, butnot limited to, W, Co, Cu, Al, doped silicon, polysilicon, silicides, orany combination thereof. Conductor layers 442 can be filled by thin filmdeposition processes, such as CVD, ALD, any other suitable process, orany combination thereof. NAND memory strings 440 can each extendvertically through alternating conductor/dielectric stack 444. In someembodiments, conductor layers 442 in alternating conductor/dielectricstack 444 are used to form the select gates and word lines for NANDmemory strings 440. At least some of conductor layers 442 in alternatingconductor/dielectric stack 444 (e.g., except the top and bottomconductor layers 442) can each be used as word lines of NAND memorystrings 440.

In some embodiments, fabrication processes to form NAND memory string440 further include forming a semiconductor channel 446 that extendsvertically through alternating conductor/dielectric stack 444. In someembodiments, fabrication processes to form NAND memory string 440further include forming a dielectric layer 448 (memory film) betweensemiconductor channel 446 and the plurality of conductor/dielectriclayer pairs in alternating conductor/dielectric stack 444. Dielectriclayer 448 can be a composite dielectric layer, such as a combination ofmultiple dielectric layers including, but not limited to, a tunnelinglayer, a storage layer, and a blocking layer.

The tunneling layer can include dielectric materials including, but notlimited to, silicon oxide, silicon nitride, silicon oxynitride, or anycombination thereof. The storage layer can include materials for storingcharge for memory operation. The storage layer materials can include,but not limited to, silicon nitride, silicon oxynitride, a combinationof silicon oxide and silicon nitride, or any combination thereof. Theblocking layer can include dielectric materials including, but notlimited to, silicon oxide or a combination of silicon oxide/siliconoxynitride/silicon oxide (ONO). The blocking layer can further include ahigh-k dielectric layer, such as an Al₂O₃ layer. Semiconductor channel446 and dielectric layer 448 can be formed by processes such as ALD,CVD, PVD, any other suitable processes, or any combination thereof.

As illustrated in FIG. 4G, a GLS 450 that extends vertically throughalternating conductor/dielectric stack 444 can be formed above siliconlayer 432. GLS 450 can include dielectric materials including, but notlimited to, silicon oxide, silicon nitride, silicon oxynitride, or anycombination thereof. GLS 450 can be formed by a dry/wet etch process toform a vertical opening through alternating conductor/dielectric stack444, followed by a fill process to fill the opening with dielectricmaterials. The opening can be filled by CVD, PVD, ALD, any othersuitable processes, or any combination thereof.

As illustrated in FIG. 4G, a TAC 452 is formed on silicon layer 432. TAC452 can extend vertically through alternating conductor/dielectric stack444. In some embodiments, the lower end of TAC 452 is formed in contactwith lower array interconnect layer 426. In some embodiments,fabrication processes to form TAC 452 include forming a vertical openingthrough alternating conductor/dielectric stack 444 by a dry/wet etchprocess, followed by filling the opening with conductor materials andother materials (e.g., dielectric materials) for isolation purposes. TAC452 can include conductor materials including, but not limited to, W,Co, Cu, Al, doped silicon, silicides, or any combination thereof. Theopening of TAC 452 can be filled with conductor materials and othermaterials by ALD, CVD, PVD, electroplating, any other suitableprocesses, or any combination thereof.

As illustrated in FIG. 4G, word line via contacts 454 are formed abovesilicon layer 432. Each word line via contact 454 can extend verticallythrough a dielectric layer. In some embodiments, the lower end of wordline via contact 454 lands on a word line of NAND memory strings 440(e.g., conductor layer 442), such that each word line via contact 454 iselectrically connected to corresponding conductor layer 442. In someembodiments, fabrication processes to form word line via contacts 454include forming a vertical opening using a dry/wet etch process,followed by filling the opening with conductor materials and othermaterials (e.g., a barrier layer, an adhesion layer, and/or a seedlayer) for conductor filling, adhesion, and/or other purposes. Word linevia contacts 454 can include conductor materials including, but notlimited to, W, Co, Cu, Al, doped silicon, silicides, or any combinationthereof. The openings of word line via contacts 454 can be filled withconductor materials and other materials by ALD, CVD, PVD,electroplating, any other suitable processes, or any combinationthereof.

As illustrated in FIG. 4H, an upper array interconnect layer 456 can beformed above alternating conductor/ dielectric stack 444 and NAND memorystrings 440. Upper array interconnect layer 456 can includeinterconnects, including interconnect lines 458 and via contacts 460 inone or more ILD layers as the BEOL interconnects of the 3D memory devicefor transferring electrical signals between the 3D memory device andperipheral circuits.

In some embodiments, upper array interconnect layer 456 includesmultiple ILD layers and interconnects therein formed in multipleprocesses. For example, interconnect lines 458 and via contacts 460 caninclude conductor materials deposited by one or more thin filmdeposition processes including, but not limited to, CVD, PVD, ALD,electroplating, electroless plating, or any combination thereof.Fabrication processes to form interconnect lines 458 and via contacts460 can also include photolithography, CMP, wet/dry etch, or any othersuitable processes. The ILD layers can include dielectric materialsdeposited by one or more thin film deposition processes including, butnot limited to, CVD, PVD, ALD, or any combination thereof. The ILDlayers and interconnects illustrated in FIG. 4H can be collectivelyreferred to as an “interconnect layer” (e.g., upper array interconnectlayer 456).

FIGS. 6A-6G illustrate a fabrication process for forming anotherexemplary 3D memory device having a shielding layer, according to someembodiments of the present disclosure. FIG. 7 is a flowchart of a method700 for forming another exemplary 3D memory device having a shieldinglayer, according to some embodiments. Examples of the 3D memory devicedepicted in FIGS. 6A-6G and FIG. 7 include 3D memory device 101 depictedin FIG. 1B. FIGS. 6A-6G and FIG. 7 will be described together. It isunderstood that the operations shown in method 700 are not exhaustiveand that other operations can be performed as well before, after, orbetween any of the illustrated operations. Further, some of theoperations may be performed simultaneously, or in a different order thanshown in FIG. 7. It is further understood that the details of similarstructures (e.g., materials, fabrication process, etc.) in both 3Dmemory devices formed by methods 500 and 700 may not be repeated below.

Referring to FIG. 7, method 700 starts at operation 702, in which aplurality of memory strings each extending vertically on a substrate areformed. To form the memory strings, an alternating conductor/dielectricstack can be formed on the substrate, and each memory string can beformed to extend vertically through the alternating conductor/dielectricstack.

As illustrated in FIG. 6A, pairs of first dielectric layer 603 andsecond dielectric layer 605 (referred to herein as “dielectric layerpairs”) are formed on a silicon substrate 601. The plurality ofdielectric layer pairs can form an alternating dielectric stack 607. Insome embodiments, each dielectric layer pair includes a layer of siliconnitride and a layer of silicon oxide formed by one or more thin filmdeposition processes.

As illustrated in FIG. 6B, NAND memory strings 609 are formed on siliconsubstrate 601 and extend vertically through an alternatingconductor/dielectric stack 613. Each first dielectric layer 603 ofalternating dielectric stack 607 can be replaced by a conductor layer611, thereby forming a plurality of conductor/dielectric layer pairs inalternating conductor/ dielectric stack 613. The replacement of firstdielectric layers 603 with conductor layers 611 can be performed bywet/dry etch of first dielectric layers 603 selective to seconddielectric layers 605 and filling the structure with conductor layers611. Conductor layers 611 can include conductor materials filled by thinfilm deposition processes. In some embodiments, fabrication processes toform NAND memory string 609 further include forming a semiconductorchannel 615 that extends vertically through alternatingconductor/dielectric stack 613 and a dielectric layer 617 (memory film)between semiconductor channel 615 and the plurality ofconductor/dielectric layer pairs in alternating conductor/dielectricstack 613. Dielectric layer 617 can be a composite dielectric layer,such as a combination of multiple dielectric layers including, but notlimited to, a tunneling layer, a storage layer, and a blocking layer.

As illustrated in FIG. 6B, a GLS 619 that extends vertically throughalternating conductor/dielectric stack 613 can be formed on siliconsubstrate 601. GLS 619 can include dielectric materials and can beformed by a dry/wet etch process to form a vertical opening throughalternating conductor/dielectric stack 613, followed by a fill processto fill the opening with the dielectric materials. Word line viacontacts 621 can be also formed on silicon substrate 601. In someembodiments, fabrication processes to form word line via contacts 621include forming a vertical opening using a dry/wet etch process,followed by filling the opening with conductor materials and othermaterials (e.g., a barrier layer, an adhesion layer, and/or a seedlayer) for conductor filling, adhesion, and/or other purposes.

Method 700 proceeds to operation 704, as illustrated in FIG. 7, in whicha first interconnect layer (e.g., an array interconnect layer) is formedabove the memory strings. The first interconnect layer can include afirst plurality of interconnects in one or more ILD layers. Asillustrated in FIG. 6C, an array interconnect layer 623 can be formedabove NAND memory strings 609. Array interconnect layer 623 can includeinterconnects, including interconnect lines 625 and via contacts 627 ofMEOL and/or BEOL in multiple ILD layers, to make electrical connectionswith NAND memory strings 609. Interconnect lines 625 and via contacts627 can include conductor materials deposited by one or more thin filmdeposition processes.

Method 700 proceeds to operation 706, as illustrated in FIG. 7, in whicha shielding layer is formed above the first interconnect layer (e.g.,the array interconnect layer). Operation 706 can include forming aconduction region and an isolation region above the first interconnectlayer. The conduction region can cover the area of the interconnects inthe first interconnect layer. In some embodiments, the conduction regionof the shielding layer covers substantially the area of the substrate.Method 700 can further include additional operation(s) to form a contact(e.g., a via contact) extending vertically through the shielding layerand in contact with the interconnects of the first interconnect layer.The contact can be electrically isolated from the conduction region inthe shielding layer by the isolation region.

As illustrated in FIG. 6D, a conductive film 629 can be formed on thetop surface of array interconnect layer 623. The conductive materials inconductive film 629 can include, but not limited to, metals, metalalloys, metal silicides, and doped semiconductors, formed by one or morethin film deposition processes. In some embodiments, depositedconductive film 629 has a thickness between about 1 nm and about 1 μm,such as between 1 nm and 1 μm. In some embodiments, deposited conductivefilm 629 has a thickness between about 1 μm and about 20 μm, such asbetween 1 μm and 20 μm. A dielectric film 631 can be formed onconductive film 629. Dielectric film 631 can include dielectricmaterials formed by thermal growth and/or one or more thin filmdeposition processes.

As illustrated in FIG. 6E, conductive film 629 can be patterned to forma shielding layer 633 having a conduction region 635 and one or moreisolation regions 637. In some embodiments, conductive film 629 ispatterned to form isolation regions 637, and the remaining conductivematerials in conductive film 629 become conduction region 635.Patterning process (e.g., photolithography and dry/wet etch) can be usedfor patterning isolation regions 637 in shielding layer 633. Isolationregions 637 can then be formed by thermal growth and/or thin filmdeposition of dielectric materials in the patterned region. Shieldinglayer 633 can be patterned to form any suitable layout in differentarrangements as described above with respect to FIG. 2 and FIGS. 3A-3B.

As illustrated in FIG. 6E, one or more via contacts 639 can be formedthrough dielectric film 631 and shielding layer 633 and in contact withinterconnects 625 and 627 in array interconnect layer 623. Via contacts639 can be electrically isolated from conduction region 635 of shieldinglayer 633 by isolation regions 637. In some embodiments, via contacts639 are formed by first patterning via holes through dielectric film 631and shielding layer 633 using patterning processes. The via holes can befilled with a conductor, a barrier layer, an adhesion layer, and/or aseed layer.

Method 700 proceeds to operation 708, as illustrated in FIG. 7, in whicha second interconnect layer (e.g., a lower peripheral interconnectlayer) is formed above the shielding layer. The second interconnectlayer can include a second plurality of interconnects in one or more ILDlayers. The conduction region of the shielding layer formed at operation706 can cover the area of the interconnects in the second interconnectlayer as well. That is, the conduction region of the shielding layer cancover the area of both the first and second interconnects in the firstand second interconnect layers. A semiconductor layer (e.g., a siliconlayer) can be formed above the second interconnect layer.

As illustrated in FIG. 6F, a lower peripheral interconnect layer 641 canbe formed above shielding layer 633. Lower peripheral interconnect layer641 can include interconnects, including interconnect lines 643 and viacontacts 645 in one or more ILD layers for backside metal routing. Insome embodiments, lower peripheral interconnect layer 641 includesmultiple ILD layers (e.g., including dielectric film 631 in FIG. 6E) andinterconnects therein formed in multiple processes. Interconnect lines643 and via contacts 645 can include conductor materials deposited byone or more thin film deposition processes.

As illustrated in FIG. 6F, a silicon layer 647 can be formed above lowerperipheral interconnect layer 641. Silicon layer 647 can includepolysilicon or amorphous silicon deposited by one or more thin filmdeposition processes. Doped regions (e.g., wells) in silicon layer 647can be formed by ion implantation and/or thermal diffusion of dopants atdesired doping concentrations. Isolation regions 649 (e.g., STIs) canalso be formed in silicon layer 647 by wet/dry etch and thin filmdeposition.

Method 700 proceeds to operation 710, as illustrated in FIG. 7, in whicha peripheral device is formed above the second interconnect layer (andthe semiconductor layer). A third interconnect layer (e.g., an upperperipheral interconnect layer) can be formed above the peripheraldevice. In some embodiments, a contact (e.g., a via contact) extendingvertically through the semiconductor layer is formed and in contact withthe second interconnect layer (e.g., the lower peripheral interconnectlayer), so that the first interconnect layer (e.g., the arrayinterconnect layer) is electrically connected to the third interconnectlayer (e.g., the upper peripheral interconnect layer).

As illustrated in FIG. 6G, a peripheral device is formed on siliconlayer 647. The peripheral device can include a plurality of transistors651 formed on silicon layer 647. An upper peripheral interconnect layer653 can be formed above transistors 651. Upper peripheral interconnectlayer 653 can include interconnects, including interconnect lines 655and via contacts 657 in one or more ILD layers as the BEOL interconnectsof the 3D memory device for transferring electrical signals between the3D memory device and peripheral circuits. In some embodiments, upperperipheral interconnect layer 653 includes multiple ILD layers andinterconnects therein formed in multiple processes. For example,interconnect lines 655 and via contacts 657 can include conductormaterials deposited by one or more thin film deposition processes.

The foregoing description of the specific embodiments will so reveal thegeneral nature of the present disclosure that others can, by applyingknowledge within the skill of the art, readily modify and/or adapt forvarious applications such specific embodiments, without undueexperimentation, without departing from the general concept of thepresent disclosure. Therefore, such adaptations and modifications areintended to be within the meaning and range of equivalents of thedisclosed embodiments, based on the teaching and guidance presentedherein. It is to be understood that the phraseology or terminologyherein is for the purpose of description and not of limitation, suchthat the terminology or phraseology of the present specification is tobe interpreted by the skilled artisan in light of the teachings andguidance.

Embodiments of the present disclosure have been described above with theaid of functional building blocks illustrating the implementation ofspecified functions and relationships thereof. The boundaries of thesefunctional building blocks have been arbitrarily defined herein for theconvenience of the description. Alternate boundaries can be defined solong as the specified functions and relationships thereof areappropriately performed.

The Summary and Abstract sections may set forth one or more but not allexemplary embodiments of the present disclosure as contemplated by theinventor(s), and thus, are not intended to limit the present disclosureand the appended claims in any way.

The breadth and scope of the present disclosure should not be limited byany of the above-described exemplary embodiments, but should be definedonly in accordance with the following claims and their equivalents.

What is claimed is:
 1. A method for forming a three-dimensional (3D)memory device, comprising: forming a peripheral device on a substrate;forming a first interconnect layer comprising a first plurality ofinterconnects above the peripheral device; forming a shielding layercomprising a conduction region above the first interconnect layer;forming a second interconnect layer comprising a second plurality ofinterconnects above the shielding layer, wherein the conduction regionof the shielding layer covers an area of the first and second pluralityof interconnects in the first and second interconnect layers; andforming a plurality of memory strings each extending vertically abovethe second interconnect layer.
 2. The method of claim 1, furthercomprising forming a first contact extending vertically through theshielding layer and in contact with the first interconnect layer and thesecond interconnect layer.
 3. The method of claim 2, wherein forming theshielding layer comprises forming an isolation region in the shieldlayer to electrically isolate the conduction region and the firstcontact.
 4. The method of claim 2, further comprising: forming asemiconductor layer above the second interconnect layer; forming analternating conductor/ dielectric stack on the semiconductor layer,wherein each of the plurality of memory strings extends verticallythrough the alternating conductor/dielectric stack; and forming a thirdinterconnect layer above the alternating conductor/dielectric stack. 5.The method of claim 4, further comprising forming a second contactextending vertically through the alternating conductor/dielectric stackand the semiconductor layer and in contact with the second interconnectlayer, so that the first interconnect layer is electrically connected tothe third interconnect layer.
 6. The method of claim 1, wherein theconduction region of the shielding layer covers substantially an area ofthe substrate.
 7. A method for forming a three-dimensional (3D) memorydevice, comprising: forming a plurality of memory strings each extendingvertically on a substrate; forming a first interconnect layer comprisinga first plurality of interconnects above the plurality of memorystrings; forming a shielding layer comprising a conduction region abovethe first interconnect layer; forming a second interconnect layercomprising a second plurality of interconnects above the shieldinglayer, wherein the conduction region of the shielding layer covers anarea of the first and second plurality of interconnects in the first andsecond interconnect layers; and forming a peripheral device above thesecond interconnect layer.
 8. The method of claim 7, further comprisingforming a first contact extending vertically through the shielding layerand in contact with the first interconnect layer and the secondinterconnect layer.
 9. The method of claim 8, wherein forming theshielding layer comprises forming an isolation region in the shieldlayer to electrically isolate the conduction region and the firstcontact.
 10. The method of claim 8, further comprising: forming analternating conductor/dielectric stack on the substrate, wherein each ofthe plurality of memory strings extends vertically through thealternating conductor/dielectric stack; and forming a third interconnectlayer above the peripheral device.
 11. The method of claim 10, furthercomprising: forming a semiconductor layer above the second interconnectlayer; and forming a second contact extending vertically through thesemiconductor layer and in contact with the second interconnect layer,so that the first interconnect layer is electrically connected to thethird interconnect layer.
 12. The method of claim 7, wherein theconduction region of the shielding layer covers substantially an area ofthe substrate.